Cho hai số phức z1 = r1.(cos phi1 + isin phi1), z2 = r2.(cos phi2 + isin phi2)

A. ${\mathrm{z}}_1{\mathrm{z}}_2=$${\mathrm{r}}_1{\mathrm{r}}_2\left[\cos \left({\mathrm{\phi }}_1{\mathrm{\phi }}_2\right)+\mathrm{isin}\left({\mathrm{\phi }}_1{\mathrm{\phi }}_2\right)\right]$

B. ${\mathrm{z}}_1{\mathrm{z}}_2=$${\mathrm{r}}_1{\mathrm{r}}_2[\cos \left({\mathrm{\phi }}_1+{\mathrm{\phi }}_2\right)$$+\mathrm{isin}\left({\mathrm{\phi }}_1+{\mathrm{\phi }}_2\right)]$

C. ${\mathrm{z}}_1{\mathrm{z}}_2=$${\mathrm{r}}_1{\mathrm{r}}_2[\sin \left({\mathrm{\phi }}_1{\mathrm{\phi }}_2\right)$$+\mathrm{icos}\left({\mathrm{\phi }}_1{\mathrm{\phi }}_2\right)]$

D. ${\mathrm{z}}_1{\mathrm{z}}_2=$${\mathrm{r}}_1{\mathrm{r}}_2[\sin \left({\mathrm{\phi }}_1+{\mathrm{\phi }}_2\right)$$+\mathrm{icos}\left({\mathrm{\phi }}_1+{\mathrm{\phi }}_2\right)]$